package com.bit.java;

import java.util.Scanner;

public class Test {

    public static int Fun(int n) {
        if(n <= 2) {                    //判断台阶的数目
            return n;
        }
        return Fun(n - 1) + Fun(n - 2);    //进行递归
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int ret = Fun(n);
        System.out.println(ret);
    }

}
